/**
 * Creates a background gradient.
 *
 * @param {Color} $bg-color The background color of the gradient
 * @param {String/List} [$type] The type of gradient to be used. Can either
 * be a String which is a predefined gradient, or it can can be a list of
 * color_stops. If none is set, it will still set the `background-color`
 * to the $background-color.
 * @param {String} [$direction=top] The direction of the gradient. Can either be
 * `top` or `left`.
 * @member Global_CSS
 */
@mixin background-gradient($bg-color, $type: $base-gradient, $direction: top) {
    background-image: none;
    background-color: $bg-color;

    @if $base-gradient != null and $bg-color != transparent {
        //color_stops
        @if type-of($type) == "list" {
            @include background-image(linear-gradient($direction, $type));
        }

        //default gradients
        @else if $type == bevel {
            @include background-image(linear-gradient($direction, color_stops(
                lighten($bg-color, 15%),
                lighten($bg-color, 8%) 30%,
                $bg-color 65%,
                darken($bg-color, 6%)
            )));
        } @else if $type == bootstrap {
            @include background-image(linear-gradient($direction, color_stops($bg-color, darken($bg-color, 5))));
        } @else if $type == glossy {
            @include background-image(linear-gradient($direction, color_stops(lighten($bg-color, 15%), lighten($bg-color, 5%) 50%, $bg-color 51%, darken($bg-color, 5%))));
        } @else if $type == recessed {
            @include background-image(linear-gradient($direction, color_stops(darken($bg-color, 10%), darken($bg-color, 5%) 10%, $bg-color 65%, lighten($bg-color, .5%))));
        } @else if $type == matte {
            @include background-image(linear-gradient($direction, color_stops(lighten($bg-color, 3%), darken($bg-color, 4%))));
        } @else if $type == matte-reverse {
            @include background-image(linear-gradient($direction, color_stops(darken($bg-color, 6%), lighten($bg-color, 4%))));
        } @else if $type == glossy-toolbar {
            @include background-image(linear-gradient($direction, color_stops(#F0F5FA, #DAE6F4 2%, #CEDDEF)));
        }

        //ext3.3 gradients
        @else if $type == panel-header {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: -0.857deg, $saturation: -1.63%, $lightness: 3.529%),
                adjust-color($bg-color, $hue: 0.158deg, $saturation: -1.21%, $lightness: 0.392%) 45%,
                adjust-color($bg-color, $hue: 1.154deg, $saturation: 0.607%, $lightness: -7.647%) 46%,
                adjust-color($bg-color, $hue: 1.154deg, $saturation: 0.607%, $lightness: -7.647%) 50%,
                adjust-color($bg-color, $hue: 1.444deg, $saturation: -1.136%, $lightness: -4.706%) 51%,
                $bg-color
            )));
        } @else if $type == tabbar {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 0.0deg, $saturation: 1.604%, $lightness: 4.706%),
                $bg-color
            )));
        } @else if $type == tab {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 1.382deg, $saturation: -18.571%, $lightness: -4.902%),
                adjust-color($bg-color, $hue: 0.43deg, $saturation: -10.311%, $lightness: -2.157%) 25%,
                $bg-color 45%
            )));
        } @else if $type == tab-active {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: -212.903deg, $saturation: -88.571%, $lightness: 6.863%),
                adjust-color($bg-color, $hue: 0.43deg, $saturation: -6.753%, $lightness: 4.706%) 25%,
                $bg-color 45%
            )));
        } @else if $type == tab-over {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 4.462deg, $saturation: -9.524%, $lightness: -3.725%),
                adjust-color($bg-color, $hue: 2.272deg, $saturation: 0.0%, $lightness: -1.569%) 25%,
                $bg-color 45%
            )));
        } @else if $type == tab-disabled {
            @include background-image(linear-gradient($direction, color_stops(
                $bg-color,
                adjust-color($bg-color, $hue: -0.267deg, $saturation: 18.571%, $lightness: 2.941%)
            )));
        } @else if $type == grid-header {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 0deg, $saturation: 0%, $lightness: 20.392%),
                adjust-color($bg-color, $hue: 220.0deg, $saturation: 5.66%, $lightness: 12.353%)
            )));
        } @else if $type == grid-header-over {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 0.175deg, $saturation: 0.967%, $lightness: 14.118%),
                adjust-color($bg-color, $hue: 0.175deg, $saturation: 0.967%, $lightness: 14.118%) 39%,
                adjust-color($bg-color, $hue: 0.372deg, $saturation: 0.101%, $lightness: 10.196%) 40%,
                adjust-color($bg-color, $hue: 0.372deg, $saturation: 0.101%, $lightness: 10.196%)
            )));
        } @else if $type == grid-row-over {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 0.175deg, $saturation: 0.967%, $lightness: 14.118%),
                $bg-color
            )));
        } @else if $type == grid-cell-special {
            @include background-image(linear-gradient(left, color_stops(
                $bg-color,
                darken($bg-color, 5)
            )));
        } @else if $type == bootstrap-button or $type == bootstrap-button-disabled {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 0deg, $saturation: 0%, $lightness: 20.392%),
                adjust-color($bg-color, $hue: 220.0deg, $saturation: 5.66%, $lightness: 12.353%)
            )));
        } @else if $type == bootstrap-button-over {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 0deg, $saturation: 0%, $lightness: 10.392%),
                adjust-color($bg-color, $hue: 220.0deg, $saturation: 5.66%, $lightness: 2.353%)
            )));
        } @else if $type == bootstrap-button-pressed {
            @include background-image(linear-gradient($direction, color_stops(
                adjust-color($bg-color, $hue: 0deg, $saturation: 0%, $lightness: 20.392%),
                adjust-color($bg-color, $hue: 220.0deg, $saturation: 5.66%, $lightness: 12.353%)
            )));
        }


        // Button bar background gradient
        @else if $type == button-primary {
            @include background-image(linear-gradient($direction, color_stops(
                $btnPrimaryBackground,
                $btnPrimaryBackgroundHighlight
            )));
        }
        // Button bar defaut
        @else if $type == button-default {
            @include background-image(linear-gradient($direction, color_stops(
                $btnBackground,
                $btnBackgroundHighlight
            )));
        }
        // Button bar danger
        @else if $type == button-danger {
            @include background-image(linear-gradient($direction, color_stops(
                $btnDangerBackground,
                $btnDangerBackgroundHighlight
            )));
        }
        // Button bar success
        @else if $type == button-success {
            @include background-image(linear-gradient($direction, color_stops(
                $btnSuccessBackground,
                $btnSuccessBackgroundHighlight
            )));
        }
        // Button bar info
        @else if $type == button-info {
            @include background-image(linear-gradient($direction, color_stops(
                $btnInfoBackground,
                $btnInfoBackgroundHighlight
            )));
        }
        // Button bar warning
        @else if $type == button-warning {
            @include background-image(linear-gradient($direction, color_stops(
                $btnWarningBackground,
                $btnWarningBackgroundHighlight
            )));
        }
        // Button bar inverse
        @else if $type == button-inverse {
            @include background-image(linear-gradient($direction, color_stops(
                $btnInverseBackground,
                $btnInverseBackgroundHighlight
            )));
        }
            
        // Progress bar background gradient
        @else if $type == progress-background {
            @include background-image(linear-gradient($direction, color_stops(
                #f5f5f5,
                #f9f9f9
            )));
        }
        // Progress bar defaut
        @else if $type == progress-default {
            @include background-image(linear-gradient($direction, color_stops(
                #149bdf,
                #0480be
            )));
        }
        // Progress bar danger
        @else if $type == progress-danger {
            @include background-image(linear-gradient($direction, color_stops(
                #ee5f5b,
                #c43c35
            )));
        }
        // Progress bar success
        @else if $type == progress-success {
            @include background-image(linear-gradient($direction, color_stops(
                #62c462,
                #57a957
            )));
        }
        // Progress bar info
        @else if $type == progress-info {
            @include background-image(linear-gradient($direction, color_stops(
                #5bc0de,
                #339bb9
            )));
        }
        // Progress bar warning
        @else if $type == progress-warning {
            @include background-image(linear-gradient($direction, color_stops(
                lighten($orange, 15%),
                $orange
            )));
        }
    }
}